K-level definitions and relevant Timed-Up-and-Go test values
| K-level | Definition | Related Timed-Up-and-Go test score (s) |
| K0 | Does not have the ability or potential to ambulate or transfer safely with or without assistance, and a prosthesis does not enhance quality of life or mobility. | <9.45* |
| K1 | Has the ability or potential to use a prosthesis for transfers or ambulation in level surfaces at a fixed cadence. Typical of the limited and unlimited household ambulator. | |
| K2 | Has the ability or potential for ambulation with the ability to transverse low-level environmental barriers such as curbs, stairs or uneven surfaces. Typical of the limited community ambulator. | |
| K3 | Has the ability or potential for ambulation with variable cadence. Typical of the community ambulator who has the ability to transverse most environmental barriers and may have vocational, therapeutic or exercise activity that demands prosthetic use beyond simple locomotion. | 9.45–12.82 |
| K4 | Has the ability or potential for prosthetic ambulation that exceeds basic ambulation skills, exhibiting high impact, stress or energy levels. Typical of the prosthetic demands of the child, active adult or athlete. | >12.82 |
*Participants with K0, K1 or K2 level were not included in the referenced study. Therefore, scores below 9.45 s were considered as having functional level below K3.